[Study on the molecular characteristics of Japanese encephalitis virus living in vector mosquitoes, in Zhejiang province, 2009 - 2010].

Objective: To investigate the molecular characteristics of Japanese encephalitis virus (JEV) living in vector mosquitoes, from Zhejiang province.

Methods: A total of 13 620 mosquitoes were collected from the monitoring stations located in Cixi city and Xianju county in Zhejiang province, in July and August, 2009 - 2010. Nucleic acid of JEV from the mosquitoes was monitored by using real-time RT-PCR. The virus strains were isolated with BHK-21 cell line, with E genes of the isolated viruses amplified, sequenced and their phylogeny and homology analyzed.

Results: The positive rates of JEV for those mosquitoes collected in the stations of Cixi and Xianju were 17.0% (27/159) and 3.4% (1/29), respectively. Twenty-two JEV strains were isolated, accounted for 15.4% among the 143 batches of mosquitoes collected in 2010. All E genes in the 6 sequenced virus isolates contained 1500 nucleotides encoding 500 amino acids, in which no inserts and deletions were identified. The identity rates of nucleotide and amino acid in E gene were 99.2% - 99.8% and 100.0% among the 6 JEV strains isolated from Zhejiang, 99.1% - 99.3% and 99.2% - 99.8% between the Zhejiang strains in 2009 - 2010 and the Zhejiang strains in 2007 - 2008, respectively, 87.6% - 88.0% and 97.8% between the 6 Zhejiang strains and the vaccine strain SA14-14-2 of JEV, respectively. The phylogeny tree of E gene indicated that the JEV isolates in Zhejiang during 2009 - 2010 was located in the branch of the genotype I.

Conclusion: Mosquitoes collected from Cixi and Xianju areas carried JEV, with the rate of JEV in Cixi higher than in Xianju. All the Zhejiang isolates in 2009 - 2010 were proven to be the genotype I of JEV.